defaultableSections example

$option_build['#settings_links'][] = $view->getExecutable()->displayHandlers->get($display['id'])->optionLink($option['setting'], $link_id, 'views-button-configure', $link_value);
      }
    }

    if (!empty($view->getExecutable()->displayHandlers->get($display['id'])->options['defaults'][$id])) {
      $display_id = 'default';
      $option_build['#defaulted'] = TRUE;
    }
    else {
      $display_id = $display['id'];
      if (!$view->getExecutable()->displayHandlers->get($display['id'])->isDefaultDisplay()) {
        if ($view->getExecutable()->displayHandlers->get($display['id'])->defaultableSections($id)) {
          $option_build['#overridden'] = TRUE;
        }
      }
    }
    $option_build['#attributes']['class'][] = Html::cleanCssIdentifier($display_id . '-' . $id);
    return $option_build;
  }

  /** * Add information about a section to a display. */
  

$build = $this->view->style_plugin->render($this->view->result);

    $this->applyDisplayCacheabilityMetadata($build);

    return $build;
  }

  /** * {@inheritdoc} */
  public function defaultableSections($section = NULL) {
    $sections = parent::defaultableSections($section);

    if (in_array($section, ['style', 'row'])) {
      return FALSE;
    }

    // Tell views our sitename_title option belongs in the title section.     if ($section == 'title') {
      $sections[] = 'sitename_title';
    }
    elseif (!$section) {
      $sections['title'][] = 'sitename_title';
    }

if ($item) {
      $handler = $executable->display_handler->getHandler($type, $id);
      if (empty($handler)) {
        $form['markup'] = ['#markup' => $this->t("Error: handler for @table > @field doesn't exist!", ['@table' => $item['table'], '@field' => $item['field']])];
      }
      else {
        $types = ViewExecutable::getHandlerTypes();
        $form['#title'] = $this->t('Configure @type: @item', ['@type' => $types[$type]['lstitle'], '@item' => $handler->adminLabel()]);

        // If this item can come from the default display, show a dropdown         // that lets the user choose which display the changes should apply to.         if ($executable->display_handler->defaultableSections($types[$type]['plural'])) {
          $section = $types[$type]['plural'];
          $form_state->set('section', $section);
          views_ui_standard_display_dropdown($form, $form_state, $section);
        }

        // A whole bunch of code to figure out what relationships are valid for         // this item.         $relationships = $executable->display_handler->getOption('relationships');
        $relationship_options = [];

        foreach ($relationships as $relationship) {
          

$types = ViewExecutable::getHandlerTypes();
    $executable = $view->getExecutable();
    if (!$executable->setDisplay($display_id)) {
      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
      return $form;
    }
    $display = &$executable->displayHandlers->get($display_id);
    $form['#title'] = $this->t('Rearrange @type', ['@type' => $types[$type]['ltitle']]);
    $form['#section'] = $display_id . 'rearrange-item';

    if ($display->defaultableSections($types[$type]['plural'])) {
      $section = $types[$type]['plural'];
      $form_state->set('section', $section);
      views_ui_standard_display_dropdown($form, $form_state, $section);
    }

    $count = 0;

    // Get relationship labels     $relationships = [];
    foreach ($display->getHandlers('relationship') as $id => $handler) {
      $relationships[$id] = $handler->adminLabel();
    }

'arguments' => ['arguments'],
      'filters' => ['filters', 'filter_groups'],
      'filter_groups' => ['filters', 'filter_groups'],
    ];

    // If the display cannot use a pager, then we cannot default it.     if (!$this->usesPager()) {
      unset($sections['pager']);
    }

    foreach ($this->extenders as $extender) {
      $extender->defaultableSections($sections, $section);
    }

    if ($section) {
      if (!empty($sections[$section])) {
        return $sections[$section];
      }
    }
    else {
      return $sections;
    }
  }

  

$types = ViewExecutable::getHandlerTypes();
    $executable = $view->getExecutable();
    if (!$executable->setDisplay($display_id)) {
      $form['markup'] = ['#markup' => $this->t('Invalid display id @display', ['@display' => $display_id])];
      return $form;
    }
    $display = $executable->displayHandlers->get($display_id);
    $form['#title'] = Html::escape($display->display['display_title']) . ': ';
    $form['#title'] .= $this->t('Rearrange @type', ['@type' => $types[$type]['ltitle']]);
    $form['#section'] = $display_id . 'rearrange-item';

    if ($display->defaultableSections($types[$type]['plural'])) {
      $section = $types[$type]['plural'];
      $form_state->set('section', $section);
      views_ui_standard_display_dropdown($form, $form_state, $section);
    }

    if (!empty($view->form_cache)) {
      $groups = $view->form_cache['groups'];
      $handlers = $view->form_cache['handlers'];
    }
    else {
      $groups = $display->getOption('filter_groups');